A foundation is an element of construction that connects a building to the ground. It can transfer loads from the building to the ground. Foundations are generally considered either shallow or deep or a combination of both depending on the ground conditions below the building.
Shallow foundations are usually embedded about a meter or so into soil.
A common type of shallow foundation is the slab or raft foundation where the weight of the building is transferred to the soil through a concrete slab placed at or near the surface. Slab foundations can be reinforced mat slabs, which range from 25 cm to several meters thick, depending on the size of the building, or post-tensioned slabs, which are typically at least 20 cm for houses, and thicker for heavier structures.
For a timber floor house foundation the usual method in New Zealand is to dig out a pit approximately 800 mm-1000 mm of earth and remove off site. The costs for disposing this soil/earth off-site can be high particularly if environmental charges are levied. This may occur in the soil has been contaminated or if cross contamination between pit soil and the environment at where it is disposed may occur. Or if soil treatment is necessary prior to disposal.
A minimum ground pressure condition is needed to ensure the foundation and structure are sufficiently supported by the ground. For example, the pit typically needs to provide 200 kPa ground conditions.
In known shallow foundation constructions, a gravel raft may be created in the pit and may be composed of compacted gravel with layers of geocloth between. Concrete may then be poured over to create a concrete slab on top of the gravel raft. This may be approximately 150-400 mm thick as an example.
Square timber foundation piles (jack studs) may be installed in the concrete as the concrete slab is being constructed. Bearers, joists, framework and/or formwork may be supported by the jack studs.
The process of creating this foundation is time consuming because of the number of steps and the often different trades or suppliers of materials being involved.
The weight of this sort of foundation for a 200 sqm house may be in the order of 240 tonne.
Typical concrete raft or slab foundations are brittle due the nature of the concrete. They are strong but not very resilient. Concrete slab foundations may also be prone to shifting and elevation by liquefaction in earthquake prone areas. This can damage the foundation.
Once a concrete slab foundation has been laid it may be very difficult to move or modify. Removal involved destruction of the foundation.
It is an object of the present invention to provide a timber pole foundation that overcomes or at least ameliorates some of the abovementioned disadvantages or which at least provides the public with a useful choice.
In this specification, where reference has been made to external sources of information, including patent specifications and other documents, this is generally for the purpose of providing a context for discussing the features of the present invention. Unless stated otherwise, reference to such sources of information is not to be construed, in any jurisdiction, as an admission that such sources of information are prior art or form part of the common general knowledge in the art.
For the purpose of this specification, where method steps are described in sequence, the sequence does not necessarily mean that the steps are to be chronologically ordered in that sequence, unless there is no other logical manner of interpreting the sequence.